ABI problem with gcc-7 on Debian

[jeroen]

We've been having trouble building the R bindings on Debian "testing" (Buster). I have arrowed it down to the std::string() coercion of the Magick::Color class.

I am unsure if this is a bug in IM or Debian or me. I know that Debian ships a reasonable old version of IM6, but perhaps we can at least point down the issue so that I can properly understand and report it.

Below a minimal example:

#include <Magick++.h>
#include <iostream>

int main(){
  Magick::Image image("logo:");
  Magick::Color col(image.fillColor());
  std::string strcol(col);
  std::cout << strcol;
  return 0;
}

The program builds fine with g++6 but with g++7 I get a linking error:

g++-6 test.cpp $(pkg-config --cflags --libs Magick++)
./a.out
> #000000000000

However with gcc 7 we get:

g++-7 test.cpp $(pkg-config --cflags --libs Magick++)
/tmp/cchhBIuN.o: In function `main':
test.cpp:(.text+0x7f): undefined reference to `Magick::Color::operator std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >() const'
collect2: error: ld returned 1 exit status

[mikayla-grace]

We had similar problems with gcc 7 under Fedora. A recent update to the compiler fixed the problem. We are compiling with g++ (GCC) 7.1.1 20170622 and your test.cpp source compiles without complaint.

[jeroen]

Debian is running 7.2 which was released Aug 14, 2017:

# g++-7 --version
g++-7 (Debian 7.2.0-1) 7.2.0
Copyright (C) 2017 Free Software Foundation, Inc.

[mikayla-grace]

The patch was just the latest update to GCC 7.1, we did not make any changes to ImageMagick. We have access to Fedora, Ubuntu, and CentOS and test.cpp works fine on all of these systems. We do not have access to a Debian system so we're not sure how we can help. It could very well be a compiler issue.

[jeroen]

Hmm I don't see any gcc 7.1.1 release on the GNU website, must have been a Fedora thing or so. I'll have to figure out what exactly they patched.

[jeroen]

This may be related to https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=871300